Originally Posted by graeme.c.payne View Post
Amp-hours are not really relevant to capacitors. It is an important rating to batteries, because batteries are a chemical process that gets less efficient as temperature goes down. Charge and discharge rates have to be controlled to avoid overheating the electrolyte solution, which can severely damage the battery. The amp-hour rating is a measure of how much current (Amperes) it can deliver to a specified load, for a specified time and under specified conditions.
A capacitor is basically two conductive films separated by an insulator. Charging time and discharge time are governed by the value of the capacitor and the resistance of the external circuits. Tweaking those values can make charge & discharge times as long or short as desired. If the terminals of a charged supercapacitor are shorted by a solid metal bar, it will try to dump all of its charge at once. DO NOT DO THIS! It can produce spectacular fireworks, flashburns, electromagnetic pulses, physical damage or even death. On the other hand while a capacitor could theoretically be charged instantaneously, practical circuits will not allow that due to the limits of materials.
The materials and circuits of a capacacitor based energy system can be adjusted to deliver whatever performance is desired, over a wide range of environmental conditions. Batteries are much more limited, especially by temperature.
But it is critical to know what a capacitor battery will replace for a car or electric vehicle? How much current for how long before being too depleted to start a car? What capacity is the linked 16v car battery?